Fig. 1 Flow sheet of the work procedure, from data assessment to an application calculation.
Edited by Klaus Hack
Material Modelling Series
The Institute of Materials, London, U.K., 1996
ISBN 0 901716 74 X
The major purpose of this book is to illustrate how thermodynamic calculations can be used as a basic tool in the development and optimization of materials and processes of many different types.
The examples selected are, to a large extent, real case studies dealt with by members of the Scientific Group Thermodata Europe, SGTE, in the course of their work.
SGTE is a consortium of European laboratories working together to develop high quality thermodynamic databases for a wide variety of inorganic and metallurgical systems. The SGTE data can be obtained via members and their agents for use with commercially available software developed by some of the members, to enable users to undertake calculations of complex chemical equilibria efficiently and reliably. The case studies presented in the book have been treated using SGTE data in combination with such software.
Members of SGTE have played a principal role in promoting the concept of 'computational thermochemistry' as a time and cost-saving basis for guiding materials processing of many different types. In addition, such calculations provide crucial process-related information regarding the nature, amounts and distribution of environmentally hazardous substances produced during the different processing stages.
While further developments in data evaluation techniques, in the modelling of different types of stable and metastable phases, in the coupling of thermodynamics and kinetics and in the scope of application software are still needed, the case studies presented in this volume demonstrate convincingly that thermochemical calculations have very great potential for providing a sound and inexpensive basis for materials and process development in many areas of technology.
The book is dedicated to Professor E. Bonnier, the first Chairman of SGTE, whose vision, continuous effort, patience and guidance through the formative years of SGTE as a European group, first as a project supported by the French CNRS and afterwards by DG XIII of the European Community, were the major inspiration for the establishment of the present, wide-reaching joint activities of SGTE members. Apart from its continuous work of thermodynamic data evaluation, SGTE now carries out its own joint research contracts and via its members and agents offers its data world-wide both on-line and in the form of packages for use with main-frames or PC computers. As an organisation, SGTE cooperates in a broader international effort to unify thermodynamic data and assessment methods.
I. Ansara
P. Spencer (Chairman)
Name Index
Subject Index
The real raison d'être for the continuation of extensive experimental research in metallurgical thermochemistry is the potential application of its principles and data to practical, in particular industrial, problems. For this purpose the gathering of raw experimental data is obviously not enough. Missing numerical information must be supplemented by estimates ... Raw data must be sifted and critically evaluated to provide for every chemical system a consistent set of thermochemical properties. ...
In practice, it is true, the knowledge of reaction rates is as important as that of equilibrium, if not more so, but the kinetic problems can only be tackled when the thermodynamic ones have been settled. It is also true that, in practice, metallurgical reactions are quite involved ... but with some effort it will be found that even complicated chemical processes may be broken up into simpler reactions which are accessible to normal thermodynamic evaluation.
The above points are made in the 5th edition of Metallurgical Thermochemistry by Kubaschewski and Alcock in 1979 [79Kub]. Elsewhere in the same book the term data-bank is used, albeit in quotation marks. Most of the statements are still relevant: computer supported calculations provide an enormous potential for the application of thermodynamic principles to the solution of practical problems. There is still the need for good estimates arising from the lack of data in certain fields of interest; and critical evaluation of raw experimental results to obtain consistent thermodynamic data sets for complete chemical systems is still of paramount importance. Nevertheless, the development of software for treating thermochemical problems has made some considerable advances in the past two decades and the questions that remain open can be tackled in a much more comprehensive way.
The enormous effort involved in data collection and evaluation as carried out for example by Kubaschewski for pure substance data and by Kaufman [78Kau] in the field of alloy phases is now a somewhat less arduous task due to the availability to thermochen-tists of the computer. This has made it possible to treat thermochemistry in a completely new way. The computer, because of its data storage and management and its 'number-crunching' capabilities, has enabled us to look at the thermochen-tistry of a system as a whole, i.e. in many cases the user needs nothing more than a list of elements in his system and the values of the global variables temperature, pressure and element concentrations to carry out a theoretical study. Calculations can then be made of the phases stable at equilibrium, their amounts and compositions, and even information about the degree of instability of the phases not present at equilibrium can be provided. The flow sheet shown in Figure I may be used to illustrate the work procedure entailed in their activities.
Fig. 1 Flow sheet of the work procedure, from data assessment to an application calculation.
SGTE is making a major effort to provide comprehensive high-quality self-consistent, computerised thermodynamic databases both for pure substances and mixtures of all types and is playing a leading role in establishing methods for data evaluation and modelling of solution phases. Software for the storage and retrieval of assessed data has been developed and there are a number of application programs to treat different aspects of chemical equilibrium [70Kau, 80Bar, 83Tur, 84Sch, 85Sun, 85Tho, 85Tur, 87Bar, 88Che, 88Din, 88Roi, 88Sun, 88Tho].
References